CA1300749C - Optical reading or writing apparatus - Google Patents
Optical reading or writing apparatusInfo
- Publication number
- CA1300749C CA1300749C CA000564172A CA564172A CA1300749C CA 1300749 C CA1300749 C CA 1300749C CA 000564172 A CA000564172 A CA 000564172A CA 564172 A CA564172 A CA 564172A CA 1300749 C CA1300749 C CA 1300749C
- Authority
- CA
- Canada
- Prior art keywords
- information
- carrying medium
- optical reading
- writing apparatus
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000003287 optical effect Effects 0.000 title claims description 46
- 238000001514 detection method Methods 0.000 claims description 26
- 238000010438 heat treatment Methods 0.000 claims description 21
- 238000001816 cooling Methods 0.000 claims description 5
- 230000005679 Peltier effect Effects 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 2
- 102100022704 Amyloid-beta precursor protein Human genes 0.000 description 2
- 101000823051 Homo sapiens Amyloid-beta precursor protein Proteins 0.000 description 2
- DZHSAHHDTRWUTF-SIQRNXPUSA-N amyloid-beta polypeptide 42 Chemical compound C([C@@H](C(=O)N[C@@H](C)C(=O)N[C@@H](CCC(O)=O)C(=O)N[C@@H](CC(O)=O)C(=O)N[C@H](C(=O)NCC(=O)N[C@@H](CO)C(=O)N[C@@H](CC(N)=O)C(=O)N[C@@H](CCCCN)C(=O)NCC(=O)N[C@@H](C)C(=O)N[C@H](C(=O)N[C@@H]([C@@H](C)CC)C(=O)NCC(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](C(C)C)C(=O)NCC(=O)NCC(=O)N[C@@H](C(C)C)C(=O)N[C@@H](C(C)C)C(=O)N[C@@H]([C@@H](C)CC)C(=O)N[C@@H](C)C(O)=O)[C@@H](C)CC)C(C)C)NC(=O)[C@H](CC=1C=CC=CC=1)NC(=O)[C@@H](NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CCCCN)NC(=O)[C@H](CCC(N)=O)NC(=O)[C@H](CC=1N=CNC=1)NC(=O)[C@H](CC=1N=CNC=1)NC(=O)[C@@H](NC(=O)[C@H](CCC(O)=O)NC(=O)[C@H](CC=1C=CC(O)=CC=1)NC(=O)CNC(=O)[C@H](CO)NC(=O)[C@H](CC(O)=O)NC(=O)[C@H](CC=1N=CNC=1)NC(=O)[C@H](CCCNC(N)=N)NC(=O)[C@H](CC=1C=CC=CC=1)NC(=O)[C@H](CCC(O)=O)NC(=O)[C@H](C)NC(=O)[C@@H](N)CC(O)=O)C(C)C)C(C)C)C1=CC=CC=C1 DZHSAHHDTRWUTF-SIQRNXPUSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- CVSVTCORWBXHQV-UHFFFAOYSA-N creatine Chemical compound NC(=[NH2+])N(C)CC([O-])=O CVSVTCORWBXHQV-UHFFFAOYSA-N 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229960003624 creatine Drugs 0.000 description 1
- 239000006046 creatine Substances 0.000 description 1
- 238000002050 diffraction method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
- G11B23/50—Reconditioning of record carriers; Cleaning of record carriers ; Carrying-off electrostatic charges
- G11B23/505—Reconditioning of record carriers; Cleaning of record carriers ; Carrying-off electrostatic charges of disk carriers
- G11B23/507—Reconditioning of record carriers; Cleaning of record carriers ; Carrying-off electrostatic charges of disk carriers combined with means for reducing influence of physical parameters, e.g. temperature change, moisture
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B17/00—Guiding record carriers not specifically of filamentary or web form, or of supports therefor
- G11B17/34—Guiding record carriers during transducing operation, e.g. for track following
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
- G11B7/0037—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with discs
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
- G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B7/095—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble
- G11B7/0956—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following specially adapted for discs, e.g. for compensation of eccentricity or wobble to compensate for tilt, skew, warp or inclination of the disc, i.e. maintain the optical axis at right angles to the disc
Abstract
ABSTRACT OF THE DISCLOSURE
An information-carrying medium having the form of a disc is rotated around a central axis. The temperature of the disc is controlled by a temperature-adjusting element facing the surface of the disc.
An information-carrying medium having the form of a disc is rotated around a central axis. The temperature of the disc is controlled by a temperature-adjusting element facing the surface of the disc.
Description
~ 3 ~ ~ 7 ~ ~
OPtical Reading or Writing Apparatus SCOPF OF THF INV~NTION
This invention relates to optical reading or writing apparatus such as an optical disc memorY for reading or writing information bY light, more particularly to the apparatus for maintaining Perpend;cularity between the information-carrying medium and the optic axis of the incident bea~ of light.
BRIEF' DESCRIPTION OF THE DRAWINGS
~ig. 1 is a cross-sectional drawing of an embodiment of lo the Present invention in an oPtical reading or writing aPParatus .
Fig. lA shows a view of the embodiment shown in Fig. 1 from the direction of the arrow C.
Fig. 2 is a cross-sectional drawing of a second 1~ embodiment of the invention.
~ig. 2A shows a view of the second embodiment shown ;n ~ig. 2 from the direction Or the arrow C.
Fig. 3 is a cross-sectional drawing of a third emdodiment of the invention.
Fig. 3A shows a view Or the third embodiment shown in ~ig. 3 from the direction of the arrow C.
Fig. 4 is a cross-sectional drawing of a fourth emdodiment of the invention.
Fig. 4A shows a view of the fourth embodiment shown in Fig. 4 from the direction of the arrow C.
.
. : .
.. ( .
1 3 ~
Fig. 5 is a cross-sectional drawing of the apparatus of the Prior art.
~ ie. G is an enlarged view of part of the aPParatus of the prior art.
BACKGROUND OF THE INV~NTION
~ ig. 5 is a cross-sectional view of an optical reading or writing aPparatus of the prior art, as Presented in Japanese Utility Model APPI ication Laid-open No. 135~17/1985 and Patent APPI ication Laid-open No. 186237/19~2. The 0 apparatus comprises: a disc-shaped information-carrYing med;um 1 that rotates around a central axis and on which information can be written and read bY means of light; a spindle moton 2 to turn t;he information-carrYing medium 1; a turntable 3 that supports the information-carrYing medium 1 1~ and transmits the revolution of the sPindle motor 2; a clamper 4 that rotates together with the information-carrying medium 1 and holds it against the turntable 3; a clamper mount 5 that suPports the clamPer 4 while Permitting it to turn freelY; a sliding base 6 free to slide in the radial direction of the information-carrYin~ medium 1; an optical head 7, mounted on the slidin~ base 6, that illuminates the information-carrying medium 1 with a light beam; a shaft 8 that suPPorts the oPtical head 7 on the sliding base 6 and enables it to be tiIted; an obiective 2~ lens g mounted on the optical head 7, for directing the light beam onto the information-carrYing medium 1. the lens .
~ 3 V ~
1 being free to move both parallel to the optic axis 10(in the focusing direction) and perpendicular to the optic axis 10 (in the tracking direction); and a tilt servo mechanism 11 for tilting the optical head 7 with the shaft 8 as a PiVot.
The optical head 7 and related components are shown in two positions in this drawing, one position near the center of the information-carrying medium 1 and one position near the circumference.
Fig~ 6 is an enlarged view showing a detection means 12 o for detecting anY deviation from perpendicularity between the optic axis 10 and the surface of the information-carrying medium 1~ The detection means 12 comPrises a light-emitting element 13. Photosensors 14 and 15. and an operational amplifier 16 for the si~nals oùtPut by the photosensors 14 and 15. The detection means 12 can be mounted on the optical head 7 with the photosensors 14 and 15 located at eq~lal distances from the light-emitting element 13. AnY inclina~ion of the detection means 12 with respect to the surface of the information-carrying medium 1 2~ causes a difference in the intensitY of light received by the two Photosensors 14 and 15. The signal output from the oPerational amPlifier 16 therefore indicates the inclination between this surface and the oPtic axis~
In an optical reading or ~riting aPparatus with the structure of the prior art as described above, the information-carrying medium 1 is held between the turntable - 3 and the clamper 4 as shown in ~ig~ 5 and rotated by the spindle motor 2. Due to shrinkage immediatelY after ~ .
3 ~
manufacture, aging changes, temperature variations, and other factors, the information-carrYing medium 1 is general 1Y warPed into a concave shaPe as shown in the drawing.
When the sliding base 6, which slides in the radial direction of the information-carrYing medium 1, reaches a osition under the non-horizontal part of the surface near the circumference of the information-carrying medium 1, the optic axis 10 of the light beam from the oPtical head 7 0 mounted on the sliding base 6 is no longer perpendicular to the recording surface of the information-carrYing medium 1.
This state is detected by the detection means 12 shown in Fig. 6. In response to the signal outPut from the operational amPlifier 16, the tilt servo mechanism 11 then oPerates to tilt the optical head 7 around the shaft 8 until perpendiculari~y between the optic axis lO and the surface of the information-carrYing medium l is restored.
If the optic axis 10 were Permitted to remain nonPerPendicular to the surface of the information-carrYing medium 1, the sPot of light would be focused onto the surface in a distorted shape. This causes such Problems as follows. Namely, in information recording, the pits (holes) representing the information would be formed inaccuratelY on the surface, and in information reading, a carrier-to-noise ratio is reduced and a number of errors is increased. It would also become difficul-t to maintain tracking control;
that is, to keeP the SPot right on the track on or from . '. `
~L3 ~ ~ 7 ~ ~
1 ~hich the information should-be recorded or reProduced. In digital optical disc sYstems using a diffraction method of tracking control to keeP the spot right on the track, there would be considerable error in writing the information signal.
Since these Problems are the result of nonperpendicularity between the optic axis 10 and the surface of the information-carrying medium 1. the tilt servo mechanism 11 tilts the optical head 7 to maintain a 0 perpendicular relationshiP. The obiective lens 9 also moves at the time of tiltine. so the distance between the obiective lens 9 and the surface of the information-carrYing medium 1 undergoes considerable variation. In Fig. 5. the distance varies bY as much as A to B between locations at which the surface of the information-carrYing medium 1 is horizontal and locations at which it is not. In comPensation for this varîation, ~he ob1;ective lens 9 is moved parallel to the oPtic axis 10 to keeP the lieht beam in focus on the recording s~rrace of lhe information-carrYing medium 1.
A Problem in the optical reading or writing apParatus of the prior art as described above is that since the objective lens 9 must be sufficientlY movable parallel to the optic axis 10 to adiust the focus, and the obiective lens 9 is mounted on the optical head 7, the optical head 7 2~ has to be fairly large. A large tilt servo mechanism 11 is also required to tilt the optical head 7. The large mass that must therefore be driven on the sliding base 6 in the '~ 3 ~ ~ 7 ~
1 radial direction of the information-carrYing medium 1 raises an obstacle to high-speed driving (high-speed access to the information).
SUMMARY O~ TIIE INVENTION
An obJect of the Present invention is to solve the problems stated above.
Another obiect of the inYention is to Provide an optical reading or writing aPParatus wherein an oPtical head is small in size and no tiIt serYo mechanism is required.
0 hence a high driving (access) speed is possible.
According to the invention. there is Provided an optical reading or writing aPParatus comprising an information-carrying medium on which information can be read or writ-ten optically, the information-carrYing medium having the form of a disc rotating around a central axis and receiving a light beam from an optical head that is driven in the radial direction of the disc, a detection means located near the information-carrying medium. for detecting the angle between the oPtic axis of the light beam and the surface of the information-carrying medium.
a temPerature-adiusting element located near and facing the surface of the information-carrYing medium, for creatine a temPerature difference between the two surfaces of the information-carrying medium and therebY causing a thermal A
~ 3 U ~7~a~3 l deformation that bends the information-carrYing medium in a desired direction, and a control circuit for receiving a signal from the detection means and controlling the temperature-adjusting element by suPPlYing energy to it in such a way as to maintain a perPendicular relationship between the surface of the information-carrYing medium and the optic axis.
In this invention, perpendicularity between the surface of the information-carrying medium and the optic axis of the o light beam incident on this surface is easilY maintained.
Besides Preventing degradation of the reading and writing characteristics of the information. this invention enables the mechanism for focusing the light beam to be simplified.
the size of the oPtical head to be reduced, and the tilting 1~ mechanism to be eliminated, thus allowin~ the oPtical reading or writing apparatus to operate with a high driving (access) sPeed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 shows a cross-sectional view of an embodiment of this invention. Fig. lA is a view of the embodiment from direction C in Fig. 1. Components numbered from 1 to 10 and 12 to 16 in these drawings are the same as in the aPParatus of the Prior art.
In this embodiment. however. the oPtical head 7 is 3 ~ ~ 7~g 0unted in a fixed Position on the sliding base 6, and the detection means 12 is located at the circumference of the information-carrYing medium 1.
There is also Provided a temPerature-adiusting element 17 for creating a temPerature difference between the two surfaces of the information-carrying medium 1, comprising in this embodiment a Pair of heating elements 17A and 17B
facing the two surfaces of the information-carrYing medium 1 near its circumference. A control circuit 18 controls the temperature-adiusting element 17 bY furnishing Power to the heating elements 17A and 17B according to a signal outPut from the operational amPlifier 16 in the detection means 12.
In the oPtical reading or ~riting apparatus constructed as described above, the disc-shaped information-carrYing lS medium 1 is held on the turntable 3 bY the clamPer 4 and rotated bY the action of the sPindle motor 2. The detection means 12 detects the downward warP of the outer Part of the information-carrying medium 1~ indicated by the dashed lines : in the drawing, and the detection signal of this warp is output from the oPerational amPlifier 16. In resPonse to this signal the control circuit 18 commands only the heating ~ element 17B situated below the information-carrying medium 1 : : to generate heat1 thus raising the lower surface of the : information-carrying medium 1 to a higher temperature than 2s the upper surface. Thermal exPansion of the lower side of the information-carrying medium 1 then causes its outer Part ' 3L3 ~ 9 to bend uPward until it reaches a flat, horizontal state.
When the information-carrYing medium 1 is horizontal and flat, the signal received from the detection means 12 causes the control circuit 18 to command the heating element 17B to s stop generating heat. The surface of the information-carrying medium 1 can be maintained in the same Plane by feedback of the outPut signal from the detection means 12 to the control circuit 18, thereby adjusting the temperature difference between the two surfaces of the information-carrying medium 1 so as to cause thermal deformation to cancel the original warP of the information-carrYing medium 1. If the surface of the information-carrying medium 1 is held in this fixed Plane, a Perpendicular angle will be maintained between the surface of the information-carrying medium 1 and the optic axis 10 of the light beam incident on it despite motion of the optical head 7 in the radial direction. Degradation of the information reading and writing characteristics is thus prevented without causing any Problems of mechanical control, and without the need for the tilt servo mechanism 11 to move the oPtical head 7 as in the Prior art. ~urthermore, since the distance A between the surface of the information-carrYing medium 1 and the objective lens 9 on the oPtical head 7 does not vary, the obiective lens 9 does not have to be moved parallel to the 2s optic axis 10 as much as in the Prior art; all that is required is a small motion to comPensate for variations in 3 V ~ 7 ~
ositional relationships and to follow the swrface deviation of the information-carrYing medium 1. The size of the focus adiusting mechanism of the obiective lens 9 can therefore be reduced, and with it the size of the oPtical head 7. As a result, the sliding base 6 can carry a much smaller mass than before, so the sliding base 6 and the oPtical head 7 can be driven at high sPeeds (enabling fast access time).
As an added effect, the temPerature-adiusting element 17 can be used to remove condensed moisture. In this case heat is generated from both the uPper and lower heating elements 17A and 17B, without deforming the information-carryin~ medium 1.
A second embodiment o~ this invention is shown in cross-sectional drawing in ~ig. 2. ~ig. 2A shows a view of the second embodiment from direction C. In this embodiment a greater number of heating elements 17A to 17D are Provided.
The heating elements 17A and 17B are disposed in a `~ radially outer region. The heating elements 17C and 17D are disposed in a radially inner reeion. The heating elements 17A to 17D can create a temPerature difference in the radial direction on one surface of the information-carrYing medium 1. enabling to afford finer control for correcting warP in the information-carrYing medium 1. For instance, it maY be so arranged that the outer Portion is heated to the temPerature higher than the inner Portion. This arrangement is advantageous where the Portion of information-carrYing . 10 ;, 3 V ~74 ~
medium 1 facin~ the outer heating elements 17A and 17B has greater warp than the portion facing the inner heating elements 17C and 17D.
The detection means 12 can be driven in the radial S direction in association with the movement of the optical head 7, for example by mounting the detection means 12 on the oPtical head 7 or the slidins base 6. In this case energizing of outer heating elements 17A and 17B are controlled in accordance wi-th the outPuts of the detection means 12 Produced when the detection means 12 is in the radiallY outer region, while energizing of inner heating elements 17C and 17D are controlled in accordance with the outputs of the detection means 12 Produced when detection means 12 is in the radiallY inner region.
Furthermore, there can be Provided two detection means located at different radial Positions. In this case, the outer heating elements 17A and 17B and the inner heating elements 17C and 17D can be controlled according to the resPective outputs from the two detection means.
A third embodiment of this invention is shown in cross-sectional drawing in Fig. 3. Fig. 3A shows a view thereof from direction C. In this embodiment the temperature-: adiusting element 17 comprises heating elements 17A and 17B
and cooling elements 17E and 17F.
The heating element 17A and the cooling element 17E are disposed to face one surface of the information-carrYing 3~
medium 1. The heating element 17B and the cooling element 17F are disposed to face the other surface of the information-carrying medium 1. The heating element 17A (or 17B) on one side of the information-carrYing medium 1 and the cooline element 17F (or 17E) on the other side of the information-carrYing medium 1 are activated simultaneouslY0 ; If the heat generation by the heating element 17A (or 17B) and the heat absorPtion bY the cooling element 17F (or 17E) are designed to be equal to each other, simultaneous use of 0 them will not change the ambient temperature~ In other words. correction of the warP can be achieved without affecting the environment.
A fourth embodiment of this invention is shown in cross-sectional drawing in Fig. ~. Fig. 4A shows a view thereof from direction C. In this embodiment the temperature-adJusting element 17 comPrises semiconductor elements 17G and 17H emPloYing the Peltier effect. The Peltier effect makes the uPPer surface of the elements 17C
and 17H into a heat source and the lower surface into a heat sink, or vice versa, depending on the direction of current flow. The ambient temPerature can therefore be held constant with onlY one tYPe of element 17C and 17H.
~. ,
OPtical Reading or Writing Apparatus SCOPF OF THF INV~NTION
This invention relates to optical reading or writing apparatus such as an optical disc memorY for reading or writing information bY light, more particularly to the apparatus for maintaining Perpend;cularity between the information-carrying medium and the optic axis of the incident bea~ of light.
BRIEF' DESCRIPTION OF THE DRAWINGS
~ig. 1 is a cross-sectional drawing of an embodiment of lo the Present invention in an oPtical reading or writing aPParatus .
Fig. lA shows a view of the embodiment shown in Fig. 1 from the direction of the arrow C.
Fig. 2 is a cross-sectional drawing of a second 1~ embodiment of the invention.
~ig. 2A shows a view of the second embodiment shown ;n ~ig. 2 from the direction Or the arrow C.
Fig. 3 is a cross-sectional drawing of a third emdodiment of the invention.
Fig. 3A shows a view Or the third embodiment shown in ~ig. 3 from the direction of the arrow C.
Fig. 4 is a cross-sectional drawing of a fourth emdodiment of the invention.
Fig. 4A shows a view of the fourth embodiment shown in Fig. 4 from the direction of the arrow C.
.
. : .
.. ( .
1 3 ~
Fig. 5 is a cross-sectional drawing of the apparatus of the Prior art.
~ ie. G is an enlarged view of part of the aPParatus of the prior art.
BACKGROUND OF THE INV~NTION
~ ig. 5 is a cross-sectional view of an optical reading or writing aPparatus of the prior art, as Presented in Japanese Utility Model APPI ication Laid-open No. 135~17/1985 and Patent APPI ication Laid-open No. 186237/19~2. The 0 apparatus comprises: a disc-shaped information-carrYing med;um 1 that rotates around a central axis and on which information can be written and read bY means of light; a spindle moton 2 to turn t;he information-carrYing medium 1; a turntable 3 that supports the information-carrYing medium 1 1~ and transmits the revolution of the sPindle motor 2; a clamper 4 that rotates together with the information-carrying medium 1 and holds it against the turntable 3; a clamper mount 5 that suPports the clamPer 4 while Permitting it to turn freelY; a sliding base 6 free to slide in the radial direction of the information-carrYin~ medium 1; an optical head 7, mounted on the slidin~ base 6, that illuminates the information-carrying medium 1 with a light beam; a shaft 8 that suPPorts the oPtical head 7 on the sliding base 6 and enables it to be tiIted; an obiective 2~ lens g mounted on the optical head 7, for directing the light beam onto the information-carrYing medium 1. the lens .
~ 3 V ~
1 being free to move both parallel to the optic axis 10(in the focusing direction) and perpendicular to the optic axis 10 (in the tracking direction); and a tilt servo mechanism 11 for tilting the optical head 7 with the shaft 8 as a PiVot.
The optical head 7 and related components are shown in two positions in this drawing, one position near the center of the information-carrying medium 1 and one position near the circumference.
Fig~ 6 is an enlarged view showing a detection means 12 o for detecting anY deviation from perpendicularity between the optic axis 10 and the surface of the information-carrying medium 1~ The detection means 12 comPrises a light-emitting element 13. Photosensors 14 and 15. and an operational amplifier 16 for the si~nals oùtPut by the photosensors 14 and 15. The detection means 12 can be mounted on the optical head 7 with the photosensors 14 and 15 located at eq~lal distances from the light-emitting element 13. AnY inclina~ion of the detection means 12 with respect to the surface of the information-carrying medium 1 2~ causes a difference in the intensitY of light received by the two Photosensors 14 and 15. The signal output from the oPerational amPlifier 16 therefore indicates the inclination between this surface and the oPtic axis~
In an optical reading or ~riting aPparatus with the structure of the prior art as described above, the information-carrying medium 1 is held between the turntable - 3 and the clamper 4 as shown in ~ig~ 5 and rotated by the spindle motor 2. Due to shrinkage immediatelY after ~ .
3 ~
manufacture, aging changes, temperature variations, and other factors, the information-carrYing medium 1 is general 1Y warPed into a concave shaPe as shown in the drawing.
When the sliding base 6, which slides in the radial direction of the information-carrYing medium 1, reaches a osition under the non-horizontal part of the surface near the circumference of the information-carrying medium 1, the optic axis 10 of the light beam from the oPtical head 7 0 mounted on the sliding base 6 is no longer perpendicular to the recording surface of the information-carrYing medium 1.
This state is detected by the detection means 12 shown in Fig. 6. In response to the signal outPut from the operational amPlifier 16, the tilt servo mechanism 11 then oPerates to tilt the optical head 7 around the shaft 8 until perpendiculari~y between the optic axis lO and the surface of the information-carrYing medium l is restored.
If the optic axis 10 were Permitted to remain nonPerPendicular to the surface of the information-carrYing medium 1, the sPot of light would be focused onto the surface in a distorted shape. This causes such Problems as follows. Namely, in information recording, the pits (holes) representing the information would be formed inaccuratelY on the surface, and in information reading, a carrier-to-noise ratio is reduced and a number of errors is increased. It would also become difficul-t to maintain tracking control;
that is, to keeP the SPot right on the track on or from . '. `
~L3 ~ ~ 7 ~ ~
1 ~hich the information should-be recorded or reProduced. In digital optical disc sYstems using a diffraction method of tracking control to keeP the spot right on the track, there would be considerable error in writing the information signal.
Since these Problems are the result of nonperpendicularity between the optic axis 10 and the surface of the information-carrying medium 1. the tilt servo mechanism 11 tilts the optical head 7 to maintain a 0 perpendicular relationshiP. The obiective lens 9 also moves at the time of tiltine. so the distance between the obiective lens 9 and the surface of the information-carrYing medium 1 undergoes considerable variation. In Fig. 5. the distance varies bY as much as A to B between locations at which the surface of the information-carrYing medium 1 is horizontal and locations at which it is not. In comPensation for this varîation, ~he ob1;ective lens 9 is moved parallel to the oPtic axis 10 to keeP the lieht beam in focus on the recording s~rrace of lhe information-carrYing medium 1.
A Problem in the optical reading or writing apParatus of the prior art as described above is that since the objective lens 9 must be sufficientlY movable parallel to the optic axis 10 to adiust the focus, and the obiective lens 9 is mounted on the optical head 7, the optical head 7 2~ has to be fairly large. A large tilt servo mechanism 11 is also required to tilt the optical head 7. The large mass that must therefore be driven on the sliding base 6 in the '~ 3 ~ ~ 7 ~
1 radial direction of the information-carrYing medium 1 raises an obstacle to high-speed driving (high-speed access to the information).
SUMMARY O~ TIIE INVENTION
An obJect of the Present invention is to solve the problems stated above.
Another obiect of the inYention is to Provide an optical reading or writing aPParatus wherein an oPtical head is small in size and no tiIt serYo mechanism is required.
0 hence a high driving (access) speed is possible.
According to the invention. there is Provided an optical reading or writing aPParatus comprising an information-carrying medium on which information can be read or writ-ten optically, the information-carrYing medium having the form of a disc rotating around a central axis and receiving a light beam from an optical head that is driven in the radial direction of the disc, a detection means located near the information-carrying medium. for detecting the angle between the oPtic axis of the light beam and the surface of the information-carrying medium.
a temPerature-adiusting element located near and facing the surface of the information-carrYing medium, for creatine a temPerature difference between the two surfaces of the information-carrying medium and therebY causing a thermal A
~ 3 U ~7~a~3 l deformation that bends the information-carrYing medium in a desired direction, and a control circuit for receiving a signal from the detection means and controlling the temperature-adjusting element by suPPlYing energy to it in such a way as to maintain a perPendicular relationship between the surface of the information-carrYing medium and the optic axis.
In this invention, perpendicularity between the surface of the information-carrying medium and the optic axis of the o light beam incident on this surface is easilY maintained.
Besides Preventing degradation of the reading and writing characteristics of the information. this invention enables the mechanism for focusing the light beam to be simplified.
the size of the oPtical head to be reduced, and the tilting 1~ mechanism to be eliminated, thus allowin~ the oPtical reading or writing apparatus to operate with a high driving (access) sPeed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 shows a cross-sectional view of an embodiment of this invention. Fig. lA is a view of the embodiment from direction C in Fig. 1. Components numbered from 1 to 10 and 12 to 16 in these drawings are the same as in the aPParatus of the Prior art.
In this embodiment. however. the oPtical head 7 is 3 ~ ~ 7~g 0unted in a fixed Position on the sliding base 6, and the detection means 12 is located at the circumference of the information-carrYing medium 1.
There is also Provided a temPerature-adiusting element 17 for creating a temPerature difference between the two surfaces of the information-carrying medium 1, comprising in this embodiment a Pair of heating elements 17A and 17B
facing the two surfaces of the information-carrYing medium 1 near its circumference. A control circuit 18 controls the temperature-adiusting element 17 bY furnishing Power to the heating elements 17A and 17B according to a signal outPut from the operational amPlifier 16 in the detection means 12.
In the oPtical reading or ~riting apparatus constructed as described above, the disc-shaped information-carrYing lS medium 1 is held on the turntable 3 bY the clamPer 4 and rotated bY the action of the sPindle motor 2. The detection means 12 detects the downward warP of the outer Part of the information-carrying medium 1~ indicated by the dashed lines : in the drawing, and the detection signal of this warp is output from the oPerational amPlifier 16. In resPonse to this signal the control circuit 18 commands only the heating ~ element 17B situated below the information-carrying medium 1 : : to generate heat1 thus raising the lower surface of the : information-carrying medium 1 to a higher temperature than 2s the upper surface. Thermal exPansion of the lower side of the information-carrying medium 1 then causes its outer Part ' 3L3 ~ 9 to bend uPward until it reaches a flat, horizontal state.
When the information-carrYing medium 1 is horizontal and flat, the signal received from the detection means 12 causes the control circuit 18 to command the heating element 17B to s stop generating heat. The surface of the information-carrying medium 1 can be maintained in the same Plane by feedback of the outPut signal from the detection means 12 to the control circuit 18, thereby adjusting the temperature difference between the two surfaces of the information-carrying medium 1 so as to cause thermal deformation to cancel the original warP of the information-carrYing medium 1. If the surface of the information-carrying medium 1 is held in this fixed Plane, a Perpendicular angle will be maintained between the surface of the information-carrying medium 1 and the optic axis 10 of the light beam incident on it despite motion of the optical head 7 in the radial direction. Degradation of the information reading and writing characteristics is thus prevented without causing any Problems of mechanical control, and without the need for the tilt servo mechanism 11 to move the oPtical head 7 as in the Prior art. ~urthermore, since the distance A between the surface of the information-carrYing medium 1 and the objective lens 9 on the oPtical head 7 does not vary, the obiective lens 9 does not have to be moved parallel to the 2s optic axis 10 as much as in the Prior art; all that is required is a small motion to comPensate for variations in 3 V ~ 7 ~
ositional relationships and to follow the swrface deviation of the information-carrYing medium 1. The size of the focus adiusting mechanism of the obiective lens 9 can therefore be reduced, and with it the size of the oPtical head 7. As a result, the sliding base 6 can carry a much smaller mass than before, so the sliding base 6 and the oPtical head 7 can be driven at high sPeeds (enabling fast access time).
As an added effect, the temPerature-adiusting element 17 can be used to remove condensed moisture. In this case heat is generated from both the uPper and lower heating elements 17A and 17B, without deforming the information-carryin~ medium 1.
A second embodiment o~ this invention is shown in cross-sectional drawing in ~ig. 2. ~ig. 2A shows a view of the second embodiment from direction C. In this embodiment a greater number of heating elements 17A to 17D are Provided.
The heating elements 17A and 17B are disposed in a `~ radially outer region. The heating elements 17C and 17D are disposed in a radially inner reeion. The heating elements 17A to 17D can create a temPerature difference in the radial direction on one surface of the information-carrYing medium 1. enabling to afford finer control for correcting warP in the information-carrYing medium 1. For instance, it maY be so arranged that the outer Portion is heated to the temPerature higher than the inner Portion. This arrangement is advantageous where the Portion of information-carrYing . 10 ;, 3 V ~74 ~
medium 1 facin~ the outer heating elements 17A and 17B has greater warp than the portion facing the inner heating elements 17C and 17D.
The detection means 12 can be driven in the radial S direction in association with the movement of the optical head 7, for example by mounting the detection means 12 on the oPtical head 7 or the slidins base 6. In this case energizing of outer heating elements 17A and 17B are controlled in accordance wi-th the outPuts of the detection means 12 Produced when the detection means 12 is in the radiallY outer region, while energizing of inner heating elements 17C and 17D are controlled in accordance with the outputs of the detection means 12 Produced when detection means 12 is in the radiallY inner region.
Furthermore, there can be Provided two detection means located at different radial Positions. In this case, the outer heating elements 17A and 17B and the inner heating elements 17C and 17D can be controlled according to the resPective outputs from the two detection means.
A third embodiment of this invention is shown in cross-sectional drawing in Fig. 3. Fig. 3A shows a view thereof from direction C. In this embodiment the temperature-: adiusting element 17 comprises heating elements 17A and 17B
and cooling elements 17E and 17F.
The heating element 17A and the cooling element 17E are disposed to face one surface of the information-carrYing 3~
medium 1. The heating element 17B and the cooling element 17F are disposed to face the other surface of the information-carrying medium 1. The heating element 17A (or 17B) on one side of the information-carrYing medium 1 and the cooline element 17F (or 17E) on the other side of the information-carrYing medium 1 are activated simultaneouslY0 ; If the heat generation by the heating element 17A (or 17B) and the heat absorPtion bY the cooling element 17F (or 17E) are designed to be equal to each other, simultaneous use of 0 them will not change the ambient temperature~ In other words. correction of the warP can be achieved without affecting the environment.
A fourth embodiment of this invention is shown in cross-sectional drawing in Fig. ~. Fig. 4A shows a view thereof from direction C. In this embodiment the temperature-adJusting element 17 comPrises semiconductor elements 17G and 17H emPloYing the Peltier effect. The Peltier effect makes the uPPer surface of the elements 17C
and 17H into a heat source and the lower surface into a heat sink, or vice versa, depending on the direction of current flow. The ambient temPerature can therefore be held constant with onlY one tYPe of element 17C and 17H.
~. ,
Claims (9)
1. An optical reading or writing apparatus comprising an information-carrying medium on which information can be read or written optically, the information-carrying medium having the form of a disc rotating around a central axis and receiving a light beam from an optical head that is driven in the radial direction of the disc, a detection means located near the information-carrying medium, for detecting the angle between the optic axis of the light beam and the surface of the information-carrying medium.
a temperature-adjusting element located near and facing the surface of the information-carrying medium, for creating a temperature difference between the two surfaces of the information-carrying medium and thereby causing a thermal deformation that bends the information-carrying medium in a desired direction, and a control circuit for receiving a signal from the detection means and controlling the temperature-adjusting element by supplying energy to it in such a way as to maintain a perpendicular relationship between the surface of the information-carrying medium and the optic axis.
a temperature-adjusting element located near and facing the surface of the information-carrying medium, for creating a temperature difference between the two surfaces of the information-carrying medium and thereby causing a thermal deformation that bends the information-carrying medium in a desired direction, and a control circuit for receiving a signal from the detection means and controlling the temperature-adjusting element by supplying energy to it in such a way as to maintain a perpendicular relationship between the surface of the information-carrying medium and the optic axis.
2. An optical reading or writing apparatus as set forth in claim 1.
wherein the temperature-adjusting element is located facing the information-carrying medium near its circumference.
wherein the temperature-adjusting element is located facing the information-carrying medium near its circumference.
3. An optical reading or writing apparatus as set forth in claim 1, wherein the detection means is located at the circumference of the information-carrying medium.
4. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element comprises a plurality of elements which are disposed at different radial positions to create a temperature difference along the radial direction on a surface of the information-carrying medium.
5. An optical reading or writing apparatus as set forth in claim 4, wherein the detection means comprises an inner means and an outer means which are Positioned in radially inner and outer regions of the information-carrying medium, respectively.
6. An optical reading or writing apparatus as set forth in claim 1, wherein the temperature-adjusting element comprises a heating element and a cooling element disposed on opposite sides of the information-carrying medium.
7. An optical reading or writing apparatus as set forth in claim 1.
wherein the temperature-adjusting element is a semiconductor element employing the Peltier effect.
wherein the temperature-adjusting element is a semiconductor element employing the Peltier effect.
8. An optical reading or writing apparatus as set forth in claim 1.
wherein the temperature-adjusting element is also used to remove condensed moisture.
wherein the temperature-adjusting element is also used to remove condensed moisture.
9. An optical reading or writing apparatus as set forth in claim 1, wherein the detection means is driven in the radial direction to detect said angle at different positions along the radial direction.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10586687 | 1987-04-28 | ||
| JP105866/87 | 1987-04-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1300749C true CA1300749C (en) | 1992-05-12 |
Family
ID=14418884
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000564172A Expired - Fee Related CA1300749C (en) | 1987-04-28 | 1988-04-14 | Optical reading or writing apparatus |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4881204A (en) |
| EP (1) | EP0289190B1 (en) |
| CA (1) | CA1300749C (en) |
| DE (1) | DE3874591T2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5051975A (en) * | 1988-02-15 | 1991-09-24 | Mitsubishi Denki Kabushiki Kaisha | Optical recording and/or reproducing apparatus having a temperature adjusting device |
| GB0229894D0 (en) | 2002-12-21 | 2003-01-29 | Ibm | Methods, apparatus and computer programs for generating and/or using conditional electronic signatures and/or for reporting status changes |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57186237A (en) * | 1981-05-12 | 1982-11-16 | Pioneer Video Corp | Crosstalk eliminating device for recorded information reproducing device |
| JPS609018U (en) * | 1983-06-24 | 1985-01-22 | パイオニア株式会社 | Optical recording information reading device |
| US4519061A (en) * | 1983-06-27 | 1985-05-21 | Eastman Kodak Company | Sealed optical disk unit, apparatus and method for debris-suppressed recording |
| JPS6020326A (en) * | 1983-07-14 | 1985-02-01 | Olympus Optical Co Ltd | Optical disk device |
| JPS60135817A (en) * | 1983-12-26 | 1985-07-19 | Mazda Motor Corp | Running guide apparatus of car |
| JPS61267944A (en) * | 1985-05-22 | 1986-11-27 | Mitsubishi Electric Corp | Recording/reproducing device for optical disk |
| JPS62137780A (en) * | 1985-12-11 | 1987-06-20 | Hitachi Ltd | Magnetic disk device |
| JPS62188035A (en) * | 1986-02-13 | 1987-08-17 | Toshiba Corp | Condensed dew removing device for optical pickup |
-
1988
- 1988-04-14 CA CA000564172A patent/CA1300749C/en not_active Expired - Fee Related
- 1988-04-19 EP EP88303494A patent/EP0289190B1/en not_active Expired - Lifetime
- 1988-04-19 DE DE8888303494T patent/DE3874591T2/en not_active Expired - Fee Related
- 1988-04-22 US US07/185,052 patent/US4881204A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0289190A3 (en) | 1991-06-19 |
| DE3874591T2 (en) | 1993-03-11 |
| US4881204A (en) | 1989-11-14 |
| EP0289190B1 (en) | 1992-09-16 |
| EP0289190A2 (en) | 1988-11-02 |
| DE3874591D1 (en) | 1992-10-22 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |